AVFMediaAssetWriter - fix potential race condition(s)

1. m_writerQueue is now shared by recorder control and asset writer
   to ensure it lives long enough.

2. m_delegate->method() calls from async block can be dangerous, since by the time
   this block is actually executed, delegate can be deleted already. This fix uses
   Q_INVOKABLE and invokeMethod with QueuedConnection instead.

3. -finishWritingWithCompletionHandler: is async and when the block finally gets
   executed, lock and 'if aborted' test are still needed.

4. Simplify the logic and reduce locking.

Change-Id: If23daf2fe22043244033427a7f6517a0fe3f23d1
Reviewed-by: Yoann Lopes <yoann.lopes@qt.io>

1 files changed, 1 insertions, 10 deletions

diff --git a/src/plugins/avfoundation/camera/avfmediarecordercontrol_ios.mm b/src/plugins/avfoundation/camera/avfmediarecordercontrol_ios.mm
index b763dbcce..73e19e683 100644
--- a/src/plugins/avfoundation/camera/avfmediarecordercontrol_ios.mm
+++ b/src/plugins/avfoundation/camera/avfmediarecordercontrol_ios.mm
@@ -86,8 +86,7 @@ AVFMediaRecorderControlIOS::AVFMediaRecorderControlIOS(AVFCameraService *service
         return;
     }
 
-    m_writer.reset([[QT_MANGLE_NAMESPACE(AVFMediaAssetWriter) alloc] initWithQueue:m_writerQueue
-                    delegate:this delegateQueue:dispatch_get_main_queue()]);
+    m_writer.reset([[QT_MANGLE_NAMESPACE(AVFMediaAssetWriter) alloc] initWithQueue:m_writerQueue delegate:this]);
     if (!m_writer) {
         qDebugCamera() << Q_FUNC_INFO << "failed to create an asset writer";
         return;
@@ -259,14 +258,6 @@ void AVFMediaRecorderControlIOS::assetWriterStarted()
     Q_EMIT statusChanged(QMediaRecorder::RecordingStatus);
 }
 
-void AVFMediaRecorderControlIOS::assetWriterFailedToStart()
-{
-}
-
-void AVFMediaRecorderControlIOS::assetWriterFailedToStop()
-{
-}
-
 void AVFMediaRecorderControlIOS::assetWriterFinished()
 {
     AVFCameraControl *cameraControl = m_service->cameraControl();